Integrated circuit memories, such as static random access memories (SRAMs) require increasingly short access times. SRAMs are often used in the portion of a processing system where speed is very important, such as in a cache memory for a microprocessor. Address transition detection is one method that has been used to decrease access times by allowing a memory access to begin as soon as a change in the address is detected. ATD decreases memory access times, and also may reduce power consumption, by providing both preconditioning signals and activation signals in the memory. ATD is generally used in a memory to provide data line precharge and equalization signals. In addition, ATD may be used for word line driving, bit line driving, data line sensing, and for data outputting.
In a memory using ATD, an address transition detector provides a pulse in response to an address change. It is typical to have a separate address transition detector for each address signal for which transitions are to be detected. For example, if a transition of the row address is to be detected, then an address transition detector is commonly used for each row address signal. The output pulses of these detectors are then summed to provide a single pulse. In this example, a single pulse is provided when a change in any row address signal is detected.
The access time of a memory using ATD is often related to the time it takes to generate an ATD pulse after an address change. The more rapidly an ATD pulse can be generated, the earlier a memory using ATD can be accessed, thus increasing the speed of the memory.